LS: Clean up hover definition logic

[mkaput]

1. Reorganized logic scaffolding to resemble RA's code.
2. Added Markdown utility and added unit tests.
3. Moved ///
   stripping into Salsa as this looks like a more proper place.
4. Converted everything to use MarkupContent,
   as using MarkedString is deprecated in protocol.
5. Added highlights for hover targets,
   now identifiers get nice background in VSCode when hovering over them.

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Stack:

• LS: Add a high-level abstraction for inspecting defs and use it in hover #5784
• Rename get_item_definition to get_item_signature #5783
• LS: Move all Salsa extensions to lang::db module #5782
• LS: Clean up hover definition logic #5780 ⬅

⚠️ Part of a stack created by spr. Do not merge manually using the UI - doing so may have unexpected results.

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This change is 

[orizi]

Reviewed 11 of 12 files at r1, 1 of 1 files at r2, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @mkaput)

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crates/cairo-lang-defs/src/db.rs line 113 at r2 (raw file):

    // TODO(mkaput): Add tests.
    // TODO(mkaput): Support #[doc] attribute. This will be a bigger chunk of work because it would
    //   be the best to convert all /// comments to #[doc] attrs before processing items by plugins,

not sure if these should be equivalent exactly - but indeed should be easily accessible.

[mkaput]

Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @mkaput)

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crates/cairo-lang-defs/src/db.rs line 113 at r2 (raw file):

Previously, orizi wrote…

not sure if these should be equivalent exactly - but indeed should be easily accessible.

In rust they are all are concatenated. You can mix ///, #[doc], //! and #![doc] on the same item and all are concatenated in source code order. Concatenation happens before macros, so macro_rules! are only seeing one #[doc] attribute when matching for example.

[orizi]

Reviewed 1 of 1 files at r3, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @mkaput)